Maintaining metallic surfaces clear and free of deposits has long been a universal problem. Metallic surfaces made from valve metal or the so-called "film forming" metals such as titanium, tantalum, zirconium, aluminum, niobium and tungsten are, under most circumstances, quite immune to normal corrosion and thus such materials are widely used as heat exchange surfaces. However, such surfaces as well as other electroconductive surfaces such as other metals or graphite are vulnerable to biofouling as well as scale which deposits interfere with the heat transfer, impede fluid control, corrode the exchanger surface, and the like. Such deposits may be of the alkaline type, such as metal carbonates, or marine growth, such as barnacles, algae and the like. All such deposits, whether they are in a soft, semi-soft, or hardened condition, must be removed for efficient heat exchange operations. Thus, once the deposits become a problem, the equipment must be shut down and operations terminated until such deposits are removed from the heat exchange surfaces. Various means of removing deposits from metallic surfaces have been employed in the past. Most prominent and still prominent today is the shutting down of such fouled equipment and either mechanically scraping the deposits therefrom or acid washing the equipment to remove such deposits. Both of these treatments require significant loss of time on-line owing to the necessary shutdown of the equipment. Where the deposits are the result of calcium and/or magnesium scale formation, water softeners and conditioners may be used to reduce the formation of scale. However, such means are quite expensive and are often incapable of completely preventing the formation of such scale deposits.
Another method of keeping the surfaces of heat exchangers clear is by continuously subjecting said surface to chlorine or sodium hypochlorite generated in situ. Such treatment will prevent the growth of algae and barnacle formation. Normally, the chlorine is added to the system although it can be manufactured in situ if the liquid used in the system is capable of passing a current and contains salt or other chlorine producer. Typical of such systems is that described in U.S. Pat. No. 3,241,512 which electrolytically prevents fouling of ship surfaces by the electrolysis of salt water to produce chlorine gas which is distributed over the boat hull keeping the surface thereof clean while removing and/or preventing barnacles, algae and other foreign and undesirable material. In this patent, copper electrodes are used which also provide dissolved copper ions which likewise assist in preventing fouling. Other prior art describe similar processes wherein dimensionally stable anodes are used for producing the chlorine in situ to prevent fouling.